$nav-color: #F90;
nav {
  $width: 100px;
  width: $width;
  height: $width;
  color: $nav-color;
  background: red;
}
#main p {
  color: #00ff00;
  width: 97%;

  .redbox {
    background-color: #ff0000;
    color: #000000;
  }
}
#main {
  width: 97%;

  p, div {
    font-size: 2em;
    a { font-weight: bold; }
  }

  pre { font-size: 3em; }
}